The present invention relates to a semiconductor device, and to, for example, a semiconductor device including an analog-to-digital converter that utilizes a ramp signal when converting pixel signals obtained from pixels into digital values.
Various types of control have often been performed by image processing. To acquire images used for the image processing, a solid state image sensor such as a complementary metal oxide semiconductor (CMOS) image sensor is used. In recent years, there has been a demand to improve the quality of images acquired by the CMOS image sensor in order to improve an accuracy of the image processing. Thus, Japanese Unexamined Patent Application Publication No. 2013-175936 discloses a technique for improving the quality of images acquired by the CMOS image sensor.
In Japanese Unexamined Patent Application Publication No. 2013-175936, a ramp wave generating unit that outputs a ramp wave voltage, and an AD conversion unit that uses the ramp wave voltage to convert input analog signals corresponding to the amount of light incident on pixels into output digital signals, are provided. According to Japanese Unexamined Patent Application Publication No. 2013-175936, the ramp wave generating unit has a first current output DA conversion circuit that generates an output current according to first digital data, and an integrator that outputs a voltage corresponding to integration of a first output current as a ramp wave voltage.